A conventional thermostatic element expands and retracts with a temperature change of fluid, such as water, and it is applied in a thermostatic controlling device or a thermostatic control valve of shower equipment so that a water supply is controlled at a set temperature.
As shown in FIGS. 1 and 2, another conventional thermostatic element disclosed in CN Publication No. 101084477A contains a metal cover 1, a sleeve 2, a filler 3 expanding and contracting, a partition disc 4, a piston 5, a wind box 6, a pad 7, and a washer 8. The metal cover 1 further includes a tubular portion 11, a bottom end 12 for closing the tubular portion 11, and a loop 13 extending outwardly from another end of the tubular portion 11. The sleeve 2 includes a central channel 21 and a seat 22 fixed in the loop 13. The filler 3 is paraffin wax filled in the tubular portion 11 of the metal cover 1 and expands and contracts with a temperature change. The partition disc 4 is disposed between the seat 22 of the sleeve 2 and the tubular portion 11 to separate the seat 22 from the filler 3. The piston 5 is mounted in the central channel 21 of the sleeve 2 and is driven by a central area of the partition disc 4, The piston 5 has one end opposite to the partition disc 4 and another end extends out of the sleeve 2 based on the temperature change and a volume change of the filler 3. The wind box 6 is driven by the piston 5 to move without deformation. The central area of the partition disc 4 drives the piston 5 via the pad 7 and the washer 8 so that the piston 5 moves along an axial line X-X of the conventional thermostatic element. The pad 7 is made of a flexible deformable elastomer and contacts with the partition disc 4. The pad 8 is located between the piston and the pad 7 and is made of polymer, such as Teflon (PTFE), so as to prevent the pad 7 from bending around the piston 5.
The filler 3 of the conventional thermostatic element is made of paraffin wax so as to drive the piston 5 to move, but a thermal conductivity coefficient of the paraffin wax is low (around 0.25 W/m·k), so when the metal cover 1 soaks in a fluid, such as water, a reaction delay happens without reacting the temperature change. To improve such a problem, heat conductive powders, such as copper powders (around 400 W/m·k), are added into the paraffin wax. However, a heterogeneous mixture of the paraffin wax and the metal powders has a physical difference, and uniformity of the heterogeneous mixture affects the performance of the thermostatic element so the paraffin wax and the metal powders have to be mixed evenly. In case the paraffin wax and the metal powders are mixed unevenly, respective thermostatic elements have different performances.
In addition, a density of the paraffin wax is about 0.8 g/cm3 greatly different from that of metal powders (for example, a density of the cooper powders is 8.94 g/cm3). Accordingly, in operation, a separated deposition of the copper powders occurs, and heat conductions and expansions and contractions of an upper end and the lower end of the filler in the metal cover are different, thus reducing service life of the conventional thermostatic element.
To overcome above-mentioned problem, the conventional thermostatic element, as illustrated in FIGS. 3 and 4, has an improved metal cover 1. The metal cover 1 has at least two cavities 14 (i.e., four cavities 14) to fill the filler 3, and the four cavities 14 connect with each other and the metal cover 1 so that external fluid or a temperature change of the water conducts heat toward the filler 3 in the four cavities 14 through the metal cover 1. Taking the filler 3 at a fixed volume and the metal cover 1 at a fixed length for example, a contacting area of the filler 3 and the four cavities 14 is increased, and a largest distance between any two particles of the paraffin wax is lowered so as to enhance heat conducting efficiency and to reduce reaction time of the thermostatic element.
Nevertheless, the four cavities 14 of the metal cover 1 can not contact with the external fluid directly, so the heat conducting efficiency is not improved greatly.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.